Light fixture



B. MOORE Nov. 11, 1958 LIGHT FIXTURE Filed May 5, 1955 RI M m 4 m W M J t e U M 5 Y ATTORNEVJ United States Patent LIGHT FIXTURE Buell Moore, Houston, Tex., assignor, by direct and mesne assignments, of twenty percent to Will F. Wilson, Houston, Tex., fifteen percent to Wilson Electrical Equipment Co., Inc., a corporation of Texas, thirtyfive percent to Dallas L. Calmes, twenty percent to Buell Moore, five percent to Glenn M. Mathews and five percent to J. G. Mullins Application May 5, 1955, Serial No. 506,115

Claims. (Cl. 249-114) This invention relates to improvements in explosionproof light fixtures.

Explosive gases in and around hazardous areas, such as gasoline refineries, require that special precautions be taken to prevent the occurrence of a spark which might ignite the gas. A potential source of sparking is light fixtures, parts of which may be accidentally broken by activity in the area or jarred loose by vibrations from heavy machinery and caused to short circuit. One attempt at rendering such light fixtures explosion-proof has involved the use of a transparent vessel or case having tightly sealed joints for enclosing the light source. Although such fixtures are designed to prevent the admission of gas from the surrounding area, they have been found to be vapor-tight only for relatively short lengths of time and thus satisfactory only in areas in which gas may accidently escape from time to time. A more common type of fixture, designed more particularly for use in areas constantly exposed to explosive gases, and thus more truly explosive-proof, provides an enclosure having ground or threaded flame-tight joints which permit the admission of gas but prevent the escape of flame from an explosion which may occur within the enclosure.

There is a decided preference for using mercury vapor type lamps for lighting purposes at industrial locations. In order to properly dissipate the heat generated by such a lamp, it was found necessary to enlarge the enclosures of the above-mentioned explosion-proof fixtures a considerable amount. The increased vapor space brought about by such enlargement necessitated, in turn, a thicker and stronger enclosure wall to withstand the greater pressures interiorly thereof. The end result was a fixture of impractical size and cost. The problem of heat dissipation is accentuated when the lamps are provided with fluorescent coatings which will break down under excessive heat. 1

An object of this invention is to provide an explosionproof light fixture capable of dissipating heat from such light sources without the necessity of enlarging the enclosure beyond practical bounds.

Another object is to provide a light fixture usable in a hazardous area constantly exposed to explosive gases with the assurance that sparking will not occur.

Still another object is to provide an explosion-proof light fixture having better light transmission properties than those heretofore known in the art.

A further object is to provide an explosion-proof light fixture in which the light source or lamp is easily and readily replaceable within its transparent enclosure and, more particularly in which the lamp may be replaced without the danger of arcing during the period of such replacement.

A still further object is to provide an explosion-proof light fixture wherein a state of disrepair which, if unattended, might otherwise permit the ignition of gases by sparking will be visually observable.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon a consideration of the written specification, the attached claims and the annexed drawings.

In the drawings, wherein like reference characters are used throughout to designate like parts:

Fig. 1 is a longitudinal sectional view of a light fixture constructed in accordance with the present invention;

Fig. 2 is a vertical cross-sectional view of the fixture of Fig. I mounted in upright position, taken substantially along broken line 22 of Fig. 1;

Fig. 3 is a plan view of the lower well portion of the fixture, taken substantially along broken line 3-3 of Fig. 2; and

Fig. 4 is a partial plan view of the top of the fixture, including the removable top of the enclosure thereof.

In accordance with the present invention, there is provided a light fixture in which all electrical contacts for the light source or lamp may be immersed within an electrically non-conductive, transparent liquid so as to prevent the occurrence of arcing therebetween. This light fixture includes an enclosure for the lamp and its contacts, including a socket for receiving the base of the lamp, which in an upright position will contain said. liquid at a level above such contacts. The enclosure comprises a vessel which is transparent at least in part and which has an opening therefrom of a size to permit said lamp to be passed therethrough. More particularly, the opening is through the upper portion of the vessel and the lamp base socket is so located with respect thereto as to permit replacement of the lamp without removal of the socket, and thus without disturbing the liquid seal about the contact elements.

The liquid contained within the vessel not only insulates the electrical contacts from one another, but also serves to cool the lamp therein. For this purpose, a liquid level is maintained for immersing at least a substantial portion of the lamp, and the liquid is of such a nature that the light transmission properties of the fixture are not impaired by such immersion.

Referring now particularly to the drawings, the light fixture of the present invention includes an enclosure 10 which is mounted within a case 11. Although the case may be eliminated and thus does not constitute an essen tial element of the present invention, it does perform certain functions in connection with the overall fixture and therefore will be described briefly below.

The case includes a curved vertical wall 12 and top and bottom walls 13 and 14, respectively, which define an open front or window 15. Opposite end portions of the wall 12 are provided with brackets 16 for suspending the case from a suitable support or holder 17, as shown in broken lines. Disposed within the case between wall 12 and the enclosure 10 is a curved reflector element 18 for directing light from the enclosure 10 out through the window 15.

Referring now more particularly to structural details of the case, the lower wall 14 is integral with curved wall 12 while the upper wall 13 comprises a separate part detachably secured to the remainder of the case by means of long bolts 19. As shown in Fig. 2, a gasket 20 may be disposed between the upper edge of wall 12 and the top wall 13 so as to provide a seal therebetween.

A section 21 of glass or other suitable transparent material is disposed .within the window 15 to provide the enclosure 10 with some element of protection against breakage and prevent the admission of foreign matter. This transparent section is held in place by means of a retainer 22 secured as at 23 to the portion of the case defining window 15 and has an aperture 24 therethrough in substantial alignment with the window 15. A sealing element 25 may be provided about the periphery of transparent section 21 for sealing between such section and the window.

The side walls of the enclosure are made up of a vertically disposed cylindrical seetion26 of suitable trans parent material which is substantially aligned with an opening 27 through the bottom wall 14 and an upwardly projecting throat 28 through upper wall 13. O-rin'gs' 29 and 30 are tightly compressed between the opposite ends of the side walls 26 of the enclosure and the top and bottom walls 13 and 14, respectively, of the case 11. The lower portion of the enclosure comprises a bowl 33 secured to lower wall 14- beneath opening 27 by means of bolts 35 which extend upwardly for connection (not shown) with top wall 13. An O-ring 36 is tightly compressed between a flange 37 on the bowl and the underside of wall 14 so as to provide a vessel for containing liquid in its upright position at a level 33, as shown in Fig; 2.

The socket 34 for receiving the base of lamp A and electrical contacts therefor are disposed within the bowl 33 and immersed within the liquid contained in the vessel at a level 38. The opening through the throat 28 at the upper portion of the vessel is closed by a readily removable cover 31 which is detachably secured to the throat by pins 32; This cover protects the interior of the enclosure against foreign matter and objects which may contaminate the liquid and break the lamp, and also prevents the accidental displacement of liquid from the bowl. For obvious reasons, the liquid level 38 is maintained beneath cover 31 to provide a vapor space therebetween.

Since, as previously mentioned, the case 11 does not constitute an essential element of the present invention, it is apparent that the enclosure 10 need not be made up of various parts of the case.

The socket 34 is a conventional type for receiving a lamp A having a screw-in type base and thus is mounted on a porcelain base 38a. As shown in Figs. 2 and 3, an electrical conduit 44 from any suitable power source is extended through the bowl 33 in sealed relation thereto by means of a conductor seal 39. As shown, the exerior portion of the conduit is insulated in the usual manner, while lead lines 41 and 42 extend within the enclosure interior for connection with contact elements 43 and 44, respectively, adjacent socket 34. As is common in fixtures of this type, the contact elements 43 and 44 are electrically connected to the terminals of the socket 34 so as to provide a circuit into which the lamp A is connected when its base is received as shown within the socket. v

In this manner, all of the electrical contact elements of the fixture are insulated from one another by the nonconductive liquid contained at a level above the socket and lamp base. Thus, no arcing may occur which might otherwise ignite gas within the vessel above the liquid level 38. Any leakage from the liquid containing portion of the vessel would be visually indicated by a lowering of the liquid level. Thus, the liquid could be brought to a predetermined level in the vessel, and the vessel either repaired or replaced upon lowering of the level.

At least a substantial portion, and preferably all, of the lamp A is immersed in the liquid so as to provide the desired cooling effect therefor. Although it is contemplated that the lamp may be of the incandescent type, this invention is particularly well suited for mercury vapor type lamps which gene-rate considerably more heat. For example, with a General Electric H 40041 400 watt mercury vapor fluorescent lamp, the particular liquid employed has been found to keep the temperature of the lamp at approximately 250 F. as compared with a temperature of approximately 600 F. without the use of a liquid. Although it is contemplated that other nonconductive liquids may be used, the one found particularly suitable for the purposes of this invention is a 4 silicone base oil known as Dow-Corning No. 200 silicone fluid.

In addition to having a high boiling point and not being readily evaporative, this silicone base oil will not discolor or break down under heat and ultra-violet light from a fluorescent mercury vapor lamp of this type. It has been determined that the liquid will remain clear and transparent when heated up to 375 F. In fact, it has been found that light transmission from the lamp is greater when it is immersed in this liquid than with the space between the lamp and vessel filled with vapor. This is thought to be true due to the higher refractive index of the liquid disposed between the glass inner faces.

It is contemplated that the side walls 26 will be of a strong, heat resistant transparent material such as Pyrex. In this connection, it will be understood that the term transparent has reference to the materials ability to transmit light, which will vary from one material and circumstance to another. It is in this same sense that transparent is used in connection with the liquid in which the lamp is immersed.

As can be seen from Fig. 2, the opening through throat 28 is of a size to permit the lamp A to be moved there'- through. Thus, with the socket 34 disposed as shown, replacement of the lamp requires only that the cover 31 0f the enclosure be removed, the used lamp removed from socket 34 and lifted out the throat 28, a new lamp passed through the throat 28 and into the socket 34, and the removable cover 31 replaced. Obviously, this re placement of the light source or lamp does not disturb in any way the liquid seal about the electrical contact elements so that there is no danger of arcing during this replacement. Not only is the cover 31 readily and easily removable, but it is contemplated that its detachable connection with the upper portion of the enclosure will not be vapor-tight so as to permit breathing within the vapor space above liquid level 38 and below the cover.

Heat dissipating means for further cooling the lamp are disposed at the upper end of the enclosure inasmuch as the heat in the liquid will rise. Thus, the removable cover 31 is provided with a series of radially extending metallic fins 45 and 46 upon its upper and lower surfaces, respectively. As shown in Fig. 2, the lower fins 46 extend below the liquid level 38 so as to provide a heat conductor for the relatively large body of liquid within the throat 28. In addition, radially extending fins v47 are provided upon the upper surface of top wall 13 in surrounding relation to the throat 28.

From the foregoing it will be seen that this invention is one well adapted to attain all. of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. i The invention having been described, what is claimed is:

1. An enclosure for a light source, comprising a vessel having a lower end and side walls providing a sealed container for liquid when the vessel is mounted in upright position, a socket within the vessel for receiving the base of a light source and positioned to immerse at least a substantial portion of said light source in the liquid when its base is so received, an opening through said upper .portion of the vessel to permit replacement of the light source, and a cover for said opening having fins depending at its underside to contact the liquid for dissipating the heat thereof.

2. An explosion-proof light fixture, comprising a vessel having a socket therein, contact elements adjacent and electrically connected to said socket, an electrical conduit extending through a wall of the vessel in sealed relation thereto, lead lines from the conduit connecting with the contact elements, a light source having its base received in the socket, and an electrically non-conductive liquid contained within the vessel at a level to immerse and thereby insulate and cool said socket, contact elements, lead lines and at least a substantial portion of the light source, said liquid and at least a portion of said vessel being transparent.

3. An explosion-proof light fixture, comprising a vessel having a socket in its lower portion, an electrical conduit sealably extending through a wall of the vessel, lead lines from the conduit connected with contact elements adjacent and electrically connected to the socket, an opening at its upper portion, and transparent side walls intermediate said upper and lower portions, a light source having its base received in said socket, and an electrically nonconductive, transparent liquid contained in said vessel in a relatively quiescent state and at a level to immerse said socket, lead lines, contact elements, and at least a substantial portion of the light source above its base when the vessel is mounted upright, the opening from the upper portion of the vessel being of a size to permit removal of the light source therethrough without removal of the socket and liquid therefrom.

4. An explosion-proof light fixture, comprising a vessel having a socket in its lower portion, an electrical conduit sealablyextending into the vessel, lead lines from the conduit connected with contact elements adjacent and electrically connected to the socket, an opening from the upper portion of the vessel, transparent side walls intermediate said upper and lower portions, a light source having its base received in said socket, an electrically non-conductive, transparent liquid contained in said vessel in a relatively quiescent state and at a level to immerse said socket, lead lines, contact elements and at least a substantial portion of the light source about its base when the vessel is mounted in an upright position, the opening at the upper portion of the vessel being of a size to permit removal of the light source therethrough without removal of the socket and liquid therefrom, and a readily removable cover for the opening adapted when disposed thereover to permit breathing from a vapor space above the liquid level within the vessel, said cover being provided with heat dissipating fins depending into the liquid in the vessel.

5. A fixture of the character defined in. claim 11, including a readily removable cover for the opening and heat dissipating fins on the cover depending into the liquid in the vessel.

References Cited in the file of this patent UNITED STATES PATENTS 459,872 Tommasi Sept. 22, 1891 1,727,185 Thornton Sept. 3, 1929 1,973,132 Wheat Sept. 11, 1934 2,295,046 Noel Sept. 8, 1942 2,295,339 Ericson Sept. 8, 1942 2,435,409 Rushton Feb. 3, 1948 2,465,296 Swiss Mar. 22, 1949 2,748,257 Bennett May 29, 1956 FOREIGN PATENTS 243,291 Great Britain Nov. 26, 1925 351,850 Great Britain July 2, 1931 638,013 Great Britain Apr. 21, 1947 

